A castor of the type described above is known in particular from the French document A-80.17455 which provides a spring strip which is curved and fixed by one end to a first part of the castor and whereof the other end forms a locking tenon intended to engage in a recess provided on a second part of the castor which is able to pivot with respect to the first part. If the fixing of the spring strip is released, the locking means no longer fulfil their function locking the pivoting movement.
EP 0 370 716, U.S. Pat. No. 4,494,272 and Japanese Patent Application 54-63958 published under Number 55 156 702 also disclose castors comprising locking means able to lock the pivoting of the fork joint by rotation of the wheel in one direction and to release the pivoting of the fork joint by rotation of the wheel in the other direction. These means necessitate a reverse rotation of the wheel to unlock the device and they comprise movable components actuated by the rotation of the wheel and are subject to fouling and wear due to friction against the wheel.